The study by Bridgham et al (2006) published in the April 7 issue of Science is the
lamest attempt yet — and perhaps the lamest attempt that’s even possible —
to deflect the problem that irreducible complexity poses for Darwinism.

The bottom line of the study is this: the authors started with a
protein which already had the ability to strongly interact with three
kinds of steroid hormones (aldosterone, cortisol, and “DOC”
[11-deoxycorticosterone]). After introducing several simple mutations the
protein interacted much more weakly with all of those steroids. In other
words, a pre-existing ability was decreased.

That’s it! The fact that this extremely modest and substantially
irrelevant study is ballyhooed with press
releases, a commentary in Science by Christoph Adami, and forthcoming
stories in the mainstream media, demonstrates the great anxiety some folks
feel about intelligent design.

In the study the authors wished to see if two related modern proteins
called the glucocorticoid (GR) receptor and mineralocorticoid receptor
(MR) could be derived from a common ancestral protein. Using clever
analysis the authors made a protein that they thought represented the
ancestral protein. That protein binds several, structurally-similar
hormones, as does modern MR. They then introduced two amino acid changes
into the protein which are found in modern GR. The two changes caused the
ancestral protein to bind the different kinds of hormones anywhere from
ten- to a thousand-fold more weakly. That protein bound aldosterone about
three-fold more weakly than cortisol. The authors note that modern GR (in
tetrapods) also binds aldosterone more weakly than cortisol. So perhaps,
the thinking goes, an ancestral gene that could bind both hormones
duplicated in the past, one copy accumulated those two mutations to become
the modern GR, and the other copy became modern MR.

Here are number of comments in response:

This continues the venerable Darwinian tradition of making grandiose
claims based on piddling results. There is nothing in the paper that an ID
proponent would think was beyond random mutation and natural selection. In
other words, it is a straw man.

The authors (including Christoph Adami in his commentary) are
conveniently defining “irreducible complexity” way, way down. I certainly
would not classify their system as IC. The IC systems I discussed in
Darwin’s Black Box contain multiple, active protein factors. Their
“system”, on the other hand, consists of just a single protein and its
ligand. Although in nature the receptor and ligand are part of a larger
system that does have a biological function, the piece of that larger
system they pick out does not do anything by itself. In other words, the
isolated components they work on are not irreducibly complex.

In the experiment just two amino acid residues were changed! No new
components were added, no old components were taken away.

Nothing new was produced in the experiment; rather, the pre-existing
ability of the protein to bind several molecules was simply weakened. The
workers begin their experiments with a protein that can strongly bind
several, structurally-very-similar steroids, and they end with a protein
that at best binds some of the steroids ten-fold more weakly. (Figure
4C)

Such results are not different from the development of antibiotic
resistance, where single amino acid changes can cause the binding of a
toxin to a particular protein to decrease (for example, warfarin
resistance in rats, and resistance to various AIDS drugs). Intelligent
design proponents happily agree that such tiny changes can be accomplished
by random mutation and natural selection.

In the “least promising” intermediate (L111Q) the protein has
essentially lost its ability to bind any steroid. In the “most promising”
intermediate protein (the one that has just the S106P alteration) the
protein has lost about 99% of its ability to bind DOC and cortisol, and
lost about 99.9% of its ability to bind aldosterone. (Figure 4C)

Although the authors imply (and Adami claims directly) that the
mutated protein is specific for cortisol, in fact it also binds
aldosterone with about half of the affinity. (Compare the red and green
curves in the lower right hand graph of Figure 4C.) What’s more, there
actually is a much larger difference (about thirty-fold) in binding
affinity for aldosterone and cortisol with the beginning, ancestral
protein than for the final, mutated protein (about two-fold). So the
protein’s ability to discriminate between the two ligands has decreased by
ten-fold.

One would think that the hundred-fold decrease in the ability to
bind a steroid would at least initially be a very detrimental change that
would be weeded out by natural selection. The authors do not test for
that; they simply assume it wouldn’t be a problem, or that the problem
could somehow be easily overcome. Nor do they test their speculation that
DOC could somehow act as an intermediate ligand. In other words, in
typical Darwinian fashion the authors pass over with their imaginations
what in reality would very likely be serious biological difficulties.

The fact that such very modest results are ballyhooed owes more, I
strongly suspect, to the antipathy that many scientists feel toward ID
than to the intrinsic value of the experiment itself.

In conclusion, the results (and even the
imagined-but-problematic
scenario) are well within what an ID proponent
already would think Darwinian processes could do, so they won’t affect our
evaluation of the science. But it’s nice to know that Science magazine is
thinking about us.